Heat exchangers used to condense a high pressure vapor refrigerant into a high pressure liquid refrigerant for an air-conditioning system are known in the art and are referred to as condensers. Condensers having an integral sub-cooler portion are known as sub-cooled condensers, which typically include a plurality of refrigerant tubes in hydraulic communication with two spaced apart headers, such as an inlet/outlet header and a return header. The tubes are divided into an upstream group and a downstream group, the latter of which is also known as the “sub-cooling” group. For condensers having an inlet/outlet header and a return header, the headers typically include an internal partition that divides each of the headers into a first chamber and a second chamber. The first chambers are in hydraulic communication with the upstream group of tubes to define a condenser portion and the second chambers are in hydraulic communication with the sub-cooling group of tubes to define a sub-cooler portion.
A high pressure vapor refrigerant enters the first chamber of the inlet/outlet header and flows through the upstream group of tubes into the first chamber of the return header. As the refrigerant flows through this condenser portion, the refrigerant is condensed, or liquefied, into a high pressure liquid refrigerant at or near its saturation temperature. The liquefied refrigerant is then directed through a receiver tank. The receiver tank may include a desiccant material to remove any water before the liquefied refrigerant enters the second chamber of the return header to be directed through the sub-cooling group of tubes. As the refrigerant flows through this sub-cooler portion, the high temperature liquid refrigerant is sub-cooled below its saturation temperature. It is known that sub-cooled refrigerant improves the overall cooling performance of an air-conditioning system.
There exists a need to provide a stable liquefied refrigerant to the sub-cooler portion of the condenser for improved sub-cooling of the refrigerant. There also exists a need to maintain a sufficient amount of refrigerant reserve in the receiver tank to account for refrigerant leakage over the operating life of the air-conditioning system while minimizing the amount of refrigerant charge in the air-conditioning system without compromising the efficiency of the air-conditioning system. There is also a further need to minimize the size and complexity of the sub-cooled condenser for ease of plumbing and assembly into a motor vehicle.